Hi Forgot to Say in my last post Welcome to the forum.
Did the dealer give you a packet with the trailer manuals for the appliances and other parts of the trailer use and care. Dexter axles is the manufacturer used on a lot of the Forest River trailer.
If you are looking for which brand of grease to buy that will bring out the pop corn and peanut gallery as every one has a different brand and price range they like. I just buy a good lithium grease that meets the temp range & pressure at the local automotive parts dealer near me.
If you are looking to use the grease zerk supplied in the axle only to grease your axle I would not do it. There a lot of post about seal failure and filling the breaks with grease with use of the grease zerk.
I repack the bearing the old school way every 1-2 years or 15000 miles of use. That way I can inspect all the parts to make sure there are no problems that will surprise me. Well lets rephrase that I try to prevent a problem by not taking a short cut in the preventive maintenance.
Hope This Helps Tim